Expression of MicroRNA-155 is Downregulated in Peripheral Blood Mononuclear Cells of Chronic Hepatitis B Patients

Persistent hepatitis B virus (HBV) infection is sustained by inadequate immune responses, either natural or acquired. Recent studies have suggested that immune responses to viral infection may be affected by microRNA (miR)-155, via its involvement in immune cell differentiation and maturation. However, little is known on the specific interaction between miR-155 and HBV in host antiviral immunity. This study evaluated the levels of miR-155 in peripheral blood mononuclear cells (PBMCs) of chronic hepatitis B (CHB) patients, relative to that of healthy subjects, and investigated an association between miR-155 levels and HBV DNA or alanine aminotransferase (ALT). Total RNA was extracted from peripheral venous blood samples of 90 treatment-naive patients with chronic HBV infection and 20 healthy volunteers. The levels of miR-155 in the PBMCs were measured by real-time quantitative polymerase chain reaction. Serum HBV DNA and liver enzymes were estimated using standard clinical laboratory methods. In the HBV-infected patients, the miR-155 levels were significantly lower than in the healthy controls (P = 0.001). Chronic HBV-infected patients with elevated ALT had higher levels of miR-155 compared with patients with normal ALT (P = 0.014). No correlations were found between miR-155 and ALT or HBV DNA. The miR-155 appeared to be suppressed during HBV infection. The significantly higher miR-155 levels in ALT-elevated patients infected with HBV suggest that miR-155 levels in PBMCs correlate with the immune state of patients with chronic HBV infection.